This invention relates to microminiature devices and, more particularly, to the fabrication of fine-line integrated-circuit devices utilizing high-resolution resists.
One technology being actively explored as a promising approach for achieving fine-line patterning of devices is X-ray lithography. An illustrative X-ray lithographic system utilized to make structures such as very-large-scale-integrated (VLSI) semiconductor devices is described in an article by M. P. Lepselter entitled "Scaling the Micron Barrier with X-Rays," Technical Digest 1980 IEDM, page 42.
Sensitive resists suitable for high resolution in X-ray lithography are known. By way of example, these include negative resists such as DCOPA (dichloro propyl acrylate and glycidyl methacrylate-co-ethyl acrylate) which is described in U.S. Pat. No. 4,225,664 and by G. N. Taylor, G. A. Coquin and S. Somekh in "Sensitive Chlorine-Containing Resists for X-Ray Lithography," Polymer Engineering and Science, Vol. 17, No. 6, pp. 420-429, 1977, and plasma-developed resists such as those described in U.S. Pat. Nos. 4,232,110 and 4,396,704 and by G. N. Taylor, T. M. Wolf and J. M. Moran in "Organosilicon Monomers for Plasma-Developed X-Ray Resists," Journal Vacuum Science Technology, Vol. 19, No. 4, pp. 872-880, November/December 1981. (Herein, a plasma-developed resist of the aforementioned type will be generically referred to as PDXR.) In pricipal, these resists (DCOPA, PDXR et al) are capable of defining micron and submicron features in VLSI devices.
In practice, however, it has been observed that the widths of irradiated features defined in the aforementioned negative X-ray resists often deviate from the widths specified by a designer and actually exposed by X-rays. In a full-field X-ray system, all the defined features on a wafer sometimes exhibit a constant deviation (enlargement) from the specified widths. In a step-and-repeat X-ray system, feature widths consistently vary over the face of the wafer, with features that were first exposed being enlarged most relative to the prescribed widths.
The aforespecified phenomena threatened to limit the use of certain high-resolution negative resists for VLSI fabrication. Accordingly, efforts have been directed by workers in the art aimed at trying to understand the phenomena and to devise a production-worthy solution to the problems caused thereby. It was recognized that such a solution, if achieved, would be an important contribution to the field of making high-quality fine-line integrated-circuit devices.